Process of using radiation-sensitive carrier body to form stamper structure and subsequent use as a stamper to make optical disks

ABSTRACT

A radiation-sensitive carrier body directly utilized as a stamper has a glass substrate, a first highly adhesive layer securely adhered to the substrate, a radiation-sensitive layer which discharges a gas component upon being irradiated with a laser beam and which locally forms a protuberance due to the absorbed energy, a second highly adhesive layer securely adhered to the specific material of the radiation-sensitive layer and which deforms in accordance with deformation of the layer, and a metal layer which has a high releasability to allow easy separation from a optical disk substrate material such as an acrylic material when the carrier body is used as a stamper substrate for manufacturing optical disks. A protuberance formed on the carrier body such as a continuous spiral protuberance allows formation of a corresponding spiral groove in the acrylic material, serving as a pre-track into which desired information will be digitally written by a user.

This is a division of application Ser. No. 535,205 filed Sept. 23, 1983.

BACKGROUND OF THE INVENTION

The present invention relates in general to an optical type recordcarrier body and, in particular, to a radiation-sensitive record carrierbody which is utilized as a stamper structure for manufacturing anoptical type data recording disk.

In order to stabilize a servo-tracking operation and to improverecording density, it is known in the prior art to form an indentationwhich serves as a track of a predetermined shape in a recording mediumsuch as an optical disk in which information is recorded digitally inaccordance with an energy beam such as a laser beam radiated thereupon.Such a track or a pre-track is formed on the surface of a recordinglayer of an optical disk as either a protuberance or a groove, and inthe form of either a continuous spiral or a discontinuous concentricpattern. The servo-tracking operation is carried out in accordance witha difference between reflectances of the track portion of the opticaldisk and the remaining flat portion thereof.

In order to manufacture a read/write optical disk having such apre-track on which desired information may be digitally recorded or fromwhich such information may be digitally reproduced by a user, a stamperhaving a surface configuration conforming to the pre-track must first beprepared. Conventionally, a master or original disk having a track isprepared Then, an electroforming technique, for example, is used toprepare a stamper structure having a surface pattern opposite to that ofthe original disk. Using this stamper, optical disks having identicalsurface configurations, that is, tracks transferred thereto from thestamper, which are the same as that of the original disk, aremanufactured. The optical disks are prepared by injection molding,compression molding or pouring of an organic resin, or by curing anultraviolet curing resin.

Conventionally, the stamper structure with a continuous spiralpre-groove or track is manufactured as follows. A chrominum film isformed on a top surface of a transparent substrate comprisingdisk-shaped glass (of, e.g., 300 mm diameter). A photoresist material isapplied by a spinner or the like to the surface of the chromium film,thus forming a photoresist film. The substrate having the photoresistfilm formed thereon in the manner described above is then rotated at apredetermined speed. A laser beam is then focused to radiate thephotoresist film of the rotating substrate so as to form a beam spot of4,000 Å or 4 μm in diameter. This laser beam is moved at a constant feedspeed along the radial direction of the rotating disk-shaped substrate.When irradiation by the laser beam is completed, the structure exposedto the laser beam is etched, thereby obtaining an original disk whichhas a continuous spiral pre-groove. The track may alternatively comprisea projection or ridge, depending on the type of photoresist material. Anelectrode is deposited on the original disk, and the obtained structureis subjected to electroforming. A disk structure having a transferredindentation of the original disk is separated therefrom to form astamper.

However, in the prior art, it is very difficult to uniformly form thespiral track portion to have a width of 1 μm and a depth of 0.08 μm overthe entire surface of the disk-shaped structure of 300 mm in diameter.In general, when the photoresist material is applied to the substrate toform a photoresist film having a thickness of the order of microns, thephotoresist film tends to partially peel off from the disk-shapedsubstrate. As a result, uniformity of the film cannot be expected. Inparticular, when the photoresist film is formed to have a thickness ofthe order of submicrons, the photoresist material must be diluted beforebeing applied to the surface of the substrate. As a result, theuniformity of the photoresist film is further degraded, and irregulardevelopment and etching occur. Nonuniformity occurring at the beginningof the stamper manufacturing process results in a definite fault in theoptical disk. In this manner, a spiral track having the dimensionsdescribed above over the entire surface of the substrate of the opticaldisk is extremely difficult to form.

Further, according to the prior art stamper, when the photoresist filmis separated from the stamper, the photoresist film may partially remainon the stamper due to baking or the like. In addition to this, since thestamper structure is prepared from an original disk, the manufacturingprocess involves a large number of steps and is complex, requiringfurther improvements.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new and improvedradiation-sensitive record carrier body which allows uniform formationof a protuberance serving as a track at high precision over its entiresurface, and which can be effectively utilized as a stamper structure.

According to the present invention, a record carrier body, which ispreferably utilized as a stamper structure for manufacturing opticaldisks, comprises a radiation-sensitive layer which absorbs energy from abeam with which the layer is irradiated and which locally expands anddeforms in accordance with the absorbed energy. This radiation-sensitivelayer is made of a specific material for absorbing the energy of aradiation beam such as a laser beam and discharging a gas component inaccordance with the absorbed energy. The carrier body on which acontinuous spiral protuberance, for example, is formed by irradiationwith an energy beam is used as a stamper structure for molding asubstrate material for optical disks. Then, an optical disk is preparedwhich has a spiral groove serving as a pre-groove track corresponding tothe pattern of the spiral protuberance. Desired information can bewritten on the track at a user side. The record carrier body of thepresent invention further comprises a substrate supporting thereon theradiation-sensitive layer; a first adhesive layer which is interposedbetween the substrate and the radiation-sensitive layer and which has anadhesion strength sufficient to effectively adhere theradiation-sensitive layer to the substrate; a metal layer which has asufficient release property from a preselected substrate material suchas a resin used in manufacturing the optical disk; and a second adhesivelayer which is interposed between the radiation-sensitive layer and themetal layer and which has an adhesion strength sufficient to effectivelyadhere the metal layer to the radiation-sensitive layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is best understood by reference to theaccompanying drawings, in which:

FIG. 1 illustrates, in schematic cross-section, some of major steps inthe manufacture of optical disks by using a stamper according to a firstembodiment of the present invention;

FIG. 2 illustrates, in schematic cross-section, some of major steps inthe manufacture of a stamper according to a second embodiment of thisinvention; and

FIGS. 3 and 4 illustrate, in schematic cross-section, some of majorsteps in the manufacture of stampers in accordance with third and fourthembodiments of the present invention, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A to 1E show main steps in the manufacture of optical disks, onand from which information can be digitally recorded or reproduced atthe user side, using as a stamper an optical type record carrier bodyaccording to the first embodiment of the present invention. Referring toFIG. 1A, a radiation-sensitive layer 10 is formed through a thin, firsthighly adhesive layer 12 over the entire surface of a disk-shapedtransparent substrate 14 made of a glass material and having a diameterof 300 mm. This layer 10 is made of a material which absorbs irradiationenergy upon being irradiated with an energy beam such as a laser beam,and generates a gas component to form a protuberance. The material forthe layer 10 is preferably selected from mixtures of one or morelow-melting point metals such as tellurium (Te), antimony (Sb), tin(Sn), bismuth (Bi), indium (In), cadmium (Cd), zinc (Zn) and lead (Pb),and one or more elements which may be readily vaporized below apredetermined temperature (e.g., about 400° C.), such as nitrogen (N),carbon (C), hydrogen (H), oxygen (O), phosphorus (P), iodine (I),bromine (Br), and sulfur (S). In this embodiment, the layer 10 ispreferably made of a mixture of a metal having a melting point of 600°C. or lower such as Te, Bi and the like and at least one elementselected from C, N, H and O.

The layer 12 interposed between the substrate 14 and theradiation-sensitive layer 10 is made of a material which has a goodadhesion strength with a material of the substrate 14 such as glass.Accordingly, the radiation-sensitive layer 10 is securely adhered to thesubstrate 14 through the layer 12 and is prevented from peeling off thesubstrate 14. This first highly adhesive layer 12 may consist of ametallic material or a dielectric material. The metallic material forthe layer 12 may be selected from titanium (Ti), chromium (Cr), aluminum(Al), magnesium (Mg), tungsten (W), molybdenum (Mo), cobalt (Co), nickel(Ni), iron (Fe), tantalum (Ta), vanadium (V), zirconium (Zr), hafnium(Hf), and a mixture thereof. The dielectric material of the layer 12 ispreferably semiconductor oxide insulating material such as SiO₂ or TeO₂.

In this embodiment, a Ti film of 300 Å thickness was formed by a knownsputtering technique as the first highly adhesive layer 12 on the glasssubstrate 14. The radiation-sensitive layer 10 was formed by the plasmasputtering technique using a gas component such as CH₃, NH₃, CO₂ or H₂in a vacuum atmosphere in which a target consisting of one of thelow-melting point metal materials as described above was placed. Forexample, a Te target was sputtered in a CH₄ gas plasma to form a Te₅₀C₃₀ H₂₀ layer 10 having a thickness of 4,000 Å on the layer 12.According to an experiment conducted by the inventors of the presentinvention, it was observed that this Te₅₀ C₃₀ H₂₀ layer 10 absorbedabout 40% of laser energy of a wavelength of 8,300 Å. When the layer 10was heated to a temperature of 150° C. or higher in the air, the layer10 emitted a gas component which had been contained therein, with aconsequent weight decrease of about 30%.

A second highly adhesive layer 16 and a highly moldable layer or highlyreleasable layer 18 were sequentially formed on the radiation-sensitivelayer 10 in the order named. The layer 16 is preferably made of chromium(Cr), titanium (Ti), molybdenum (Mo), tungsten (W), iron (Fe), cobalt(Co), nickel (Ni), or a mixture thereof. The highly releasable layer 18is made of a material such as gold (Au), silver (Ag) or palladium (Pd)which has a relatively small adhesion strength with a transparentorganic material as the optical disk substrate material, such aspolymethyl acrylate, polycarbonate or an epoxy resin. The layers 16 and18 are formed by sputtering to have a thickness of, for example, 300 Åand 200 Å, respectively.

A record carrier body 20 having the stack structure as described aboveis securely fixed on a rotatable support table 22, as shown in FIG. 1B.While the record carrier body 20 is rotated at a linear speed of 4 m/secby the table 22, the body 20 is irradiated with an argon laser beam 24.The laser beam 24 is focused by a known lens 26 to form a beam spothaving a predetermined spot diameter of, for example, 1 μm on the topsurface of the body 20. Referring to FIG. 1B, the laser beam 24 isscanned at a predetermined speed in the radial direction of the recordcarrier body 20 as indicated by arrow 28 so that the beam spot focusedon the body surface forms a continuous spiral track. The laser beam 24was a continuous modulation beam. The power of the laser beam 24 was setto reach 4 mW at the surface of the layer 18 of the body 20 such thatthe radiation-sensitive layer 10 could not be locally heated to form ahole.

The focused laser beam 24 is transmitted through the layers 16 and 18and radiates the underlying radiation-sensitive layer 10. As a result,in the body portion which is irradiated with the continuous beam, thelayer 10 generates a gas component contained therein to form acontinuous spiral protuberance 30, as shown in FIG. 1C. Upon this localexpansion of the layer 10, the overlying layers 16 and 18 also form acorresponding configuration. Thus, a continuous spiral protuberance 32having a uniform height of 0.1 μm and a bottom width of 1 μm is formedon the top surface of the record carrier body 20. This was confirmed bya scanning electron microscope.

Conventionally, a stamper is newly prepared using as a master astructure 20' thus obtained as shown in FIG. 1C. However, according tothe present invention, the structure 20' is directly utilized as astamper for manufacturing optical disks.

As shown in FIG. 1D, a plate 33 made of an acrylic resin is in tightcontact with the surface of the record carrier body 20' as a stamper onwhich the continuous spiral protuberance 32 is formed. An ultravioletcuring resin is then introduced between the plate 33 and the stamper 20'to provide an ultraviolet curing resin layer 35. When ultraviolet curingis performed, a substrate 34 (including the plate 33 and the layer 35)for an optical disk (FIG. 1E) is obtained, a surface configuration ofwhich is transferred thereto from the stamper 20'. The substrate 34 hasa spiral groove 36 serving as a pre-groove which corresponds to thespiral protuberance 32 of the stamper 20'. A metal film 38 correspondingto a recording layer is uniformly deposited on the substrate 34, asshown in FIG. 1E. Thus, an optical disk 40 is finally obtained which iscapable of recording or reproducing information. It should be noted thatthe substrate 34 may be obtained by using another method including thesteps of introducing an acrylic-type thermal curing resin between thebody 20' and a metal mold and performing heat curing.

According to the first embodiment of the present invention, theradiation-sensitive layer 10, which absorbs beam energy to discharge agas component contained therein in accordance with the energy absorbed,is provided to prepare a stamper 20' with the continuous spiralprotuberance 32, without using the photoresist film used in the priorart. Therefore, unlike a conventional stamper prepared by theelectroforming technique from an original disk formed by the photoresistmethod, even if the track size is as small as 0.1 μm in depth and 1 μmin width or is even smaller, highly precise tracks can be easily formedover the entire surface of the stamper 20'. Thus, the track pitch can bedecreased, thereby further increasing the recording density of opticaldisks which are obtained using the stamper 20'.

Furthermore, since the radiation-sensitive layer 10 is securely adheredto the stamper substrate 14 by the first highly adhesive layer 12, thelayer 10 may not peel off from the stamper substrate 14 when the opticaldisk substrate 34 is separated from the stamper 20'. The second highlyadhesive layer 16 formed on the radiation-sensitive layer 10 retainswell the shape of the protuberance 30 formed in the radiation-sensitivelayer 10 and also serves as a protective film which protects theradiation-sensitive layer 10 from any damage while the optical disksubstrate 34 with the pre-groove 36 is being manufactured. Accordingly,a stamper 20' having an excellent track shape and a long life can berealized. Since the highly releasable layer 18 is made of a materialwhich has a small adhesion strength with the organic resin of theoptical disk substrate 34, it facilitates easy separation of thesubstrate 34 from the stamper structure 20'. Accordingly, this preventsany part of the substrate 34 from being left on the stamper surface.Thus, the reliability of the stamper 20' is improved.

Unlike the conventional method wherein an original optical disk is firstprepared and a stamper is then prepared from the original optical diskby the electro-forming technique, in the structure of the presentinvention, a record carrier body on which a track is formed by laserbeam irradiation is used as a stamper. Therefore, the manufacturingprocess is simplified according to the present invention.

A second embodiment of the present invention will now be described withreference to FIGS. 2A to 2C. In a disk-shaped body 50 shown in FIG. 2A,similar parts to those of the body 20 shown in FIG. 1A are denoted bythe same reference numerals, and a detailed description thereof will beomitted.

An organic resin film 52 is deposited on the radiation-sensitive layer10. The material of the film 52 is preferably a material whicheffectively transmits an energy beam adopted (a laser beam in thisembodiment), which has a relatively low thermal deformationinitialization temperature, and which has excellent mechanicalelongation. Examples of such an organic resin may includepolytetrafluoroethylene, polycarbonate, polypropylene, polyethylene,polyvinyl chloride, nylon and the like, which have thermal deformationinitialization temperatures of 110° C., 130° C., 80° C., 70° C., 60° C.and 80° C., respectively, and have elongations of 80 to 250%, 100 to130%, 200 to 400%, 90 to 800%, 300 to 400% and 300 to 400%,respectively. The organic resin film 52 of a selected resin can beformed by sputtering a target of the selected resin in a gas plasma ofAr or the like or by a thin film forming technique such as vacuumdeposition. The film 52 may also be formed by plasma polymerization of amonomer gas. The film 52 shown in FIG. 2A was made ofpolytetrafluoroethylene.

The organic resin film 52 preferably has a thickness of 50 to 1,000 Å.If the thickness of the film 52 exceeds 1,000 Å, the gas componentdischarged from the layer 10 is largely absorbed within the film 52 anda desired protuberance having a height of 0.1 μm or more cannot beformed. Uniform formation of an organic thin film having a thickness of1,000 Å can be performed by a thin film forming technique in a vacuum.

As another example of the embodiment shown in FIG. 2A, a Te₅₀ C₃₀ H₁₅ N₅film of 3,500 Å thickness as the radiation-sensitive layer 10 and apolytetrafluoroethylene film of 200 Å thickness as the organic resinfilm 52 were sequentially stacked on the first highly adhesive layer 12on the glass substrate 14. In this case, the Te₅₀ C₃₀ H₁₅ N₅ film wasformed by sputtering a Te target in a gas plasma of a gas mixturesubstantially consisting of CH₄ gas and NH₃ gas in the mixing ratio of4:1. The polytetrafluoroethylene film was formed by sputtering a targetof the selected resin in an Ar gas plasma. In the Ar gas plasmasputtering, sputtering must be performed in the same vacuum chamberimmediately after the film 52 is formed on the radiation-sensitive layer10. Then, the films formed may not be subject to any adverse effect fromdust in the air. The film 52 may be an Au film having a thickness of 300Å in place of an organic resin film. However, when Ar laser beamirradiation (4,500 Å wavelength) is performed as energy beamirradiation, such an Au film reflected about 50% of the incident lightand the laser energy absorbed in the layer 10 remained only 18% theoriginal amount. In contrast to this, when the film 52 was made oftransparent polytetrafluoroethylene, the ratio of the laser energyabsorbed by the underlying layer 10 was increased to about 50%.Accordingly, the present inventors have concluded that the film 52 ispreferably made of polytetrafluoroethylene.

The disk-shaped body 50 shown in FIG. 2A is subjected to continuouslaser beam irradiation in a similar manner to that of the firstembodiment shown in FIG. 1B. As a result, a continuous spiralprotuberance 54 having a height of 0.1 μm and a width of 1 μm wasuniformly formed over the entire surface of the body 50, as shown inFIG. 2B.

The present inventors prepared five disk-shaped bodies each having thestructure as shown in FIG. 2A and having a film 52 comprising one offive different materials, respectively. More specifically, films 52 ofpolycarbonate, polypropylene, polyethylene, polyvinyl chloride, andnylon each having a thickness of 200 Å were formed onradiation-sensitive layers 10 consisting of Te₅₀ C₃₀ H₂₀ and having athickness of 4,000 Å. The Te₅₀ C₃₀ H₂₀ films were formed by sputtering aTe target in a CH₄ gas plasma, and the overlying resin films 52 wereformed by vacuum deposition. When these disk-shaped bodies wereirradiated with a laser beam in the same manner as described above,continuous spiral protuberances of excellent shape were formed inrespective cases. The body having the film 52 of polycarbonate andsubjected to a laser beam power of 4 mW had a protuberance height of0.09 μm. The body having the film 52 of polypropylene and subjected to alaser beam power of 3.5 mW had a protuberance height of 0.08 μm. Thebody having the film 52 of polyethylene and subjected to a laser beampower of 3.5 mW had a protuberance height of 0.08 μm. The body havingthe film 52 of polyvinyl chloride and subjected to a laser beam power of3.5 mW had a protuberance height of 0.07 μm. The body having the film 52of nylon and subjected to a laser beam power of 4 mW had a protuberanceheight of 0.07 μm.

Subsequently, a second highly adhesive layer 16 and a highly releasablelayer 18 similar to those in the first embodiment are sequentiallyformed on an obtained structure 50' shown in FIG. 2B. Thus, as shown inFIG. 2C, a stamper structure 56 is obtained. A manufacturing process ofoptical disks using this stamper structure 56 is similar to that of thefirst embodiment and will not be repeated.

According to the second embodiment of the present invention, a similareffect to that obtained in the first embodiment is obtained.Furthermore, according to the second embodiment, the radiation-sensitivelayer 10 and the organic resin film 52 may be easily formed by aconventional thin film forming process such as sputtering, evaporation,or the like. Accordingly, the films may be respectively formed to have auniform thickness in a clean atmosphere containing none of theimpurities found in the air such as dust, while preventing separation ofthe formed film. The thin film 52 of, for example, an organic resin isformed on the radiation-sensitive layer 10. The gas component locallydischarged from the layer 10 upon laser irradiation is trapped beneaththe thin film 52, and the protuberance portion is formed in the film 52by the gas pressure. The protuberance 54 formed on the body 50' can beeffectively controlled to have a required shape (height, width). Forthis reason, a spiral protuberance 58 of a stamper structure 56 to bemanufactured thereafter can be precisely controlled.

A third embodiment of the present invention will now be described withreference to FIGS. 3A to 3C. A disk-shaped body 100 illustrated in FIG.3A has a metal film 102 which is formed on an organic resin film 52 andwhich has a good elongation characteristic. The metal film 102 ispreferably made of at least one material selected from the groupconsisting of gold (Au), titanium (Ti), chromium (Cr), platinum (Pt),palladium (Pd), silver (Ag), tantalum (Ta), molybdenum (Mo), zirconium(Zr), and the like. The metal film 102 is formed by sputtering in an Argas plasma using the metallic material as a target, or by a thin filmforming technique such as vacuum deposition.

In the same manner as in the process shown in FIG. 1B of the firstembodiment, the structure shown in FIG. 3A is subjected to laserirradiation. Then, a disk-shaped body 100' having a continuous spiralprotuberance 104 is obtained, as shown in FIG. 3B. The protuberance 104is formed in, for example, the Au film 102 since the organic resin film52 itself partially decomposes to discharge a gas component whereby thegas pressure deforms the film 102. The Au film 102 easily deforms due tothe gas pressure discharged from the underlying films 10 and 52 uponlaser irradiation, and forms the continuous spiral track 104.Thereafter, a second highly adhesive layer 16 and a highly releasablelayer 18 are sequentially formed on the structure 100' shown in FIG. 3B,to obtain a stamper structure 106 with a continuous spiral protuberance108 shown in FIG. 3C. The process for manufacturing optical disks usingthis stamper 106 is similar to that of the embodiments described above,and will not be repeated.

According to the third embodiment, the film 102, which is made of ametal such as Au having an excellent elongation characteristic and whicheasily deforms into a protruding shape, is additionally formed on theorganic resin film 52. Accordingly, the shape of the protuberance 104 ofthe disk-shaped body 100 can be made to remain stable even after timehas elapsed (semipermanent) in accordance with the laser irradiation.The life of the stamper 106 to be manufactured later is prolonged andthe reliability thereof is improved.

According to a fourth embodiment of the present invention, a disk-shapedbody 150 has two metal films 152 and 154 on a radiation-sensitive layer10 formed on a substrate 14 through a first highly adhesive layer 12, asshown in FIG. 4A. The radiation-sensitive layer 10 comprises, forexample, a Te₅₀ C₃₀ H₁₅ N₅ film having a thickness of 3,500 Å. The firstmetal film 152 formed directly on the layer 10 is preferably made of ametallic material containing at least one metal having a relatively highcoefficient of thermal expansion, such as zinc (Zn), antimony (Sb),cadmium (Cd), thallium (Tl), magnesium (Mg), aluminum (Al), manganese(Mn), and silver (Ag). The first metal film 152 can be easily formed bysputtering of a target of the selected metallic material in an Ar gasplasma, or by vacuum deposition. The second metal film 154 is preferablymade of a metallic material containing at least one metal having arelatively small coefficient of thermal expansion and a good mechanicalelongation characteristic, such as gold (Au), palladium (Pd), platinum(Pt), titanium (Ti), chromium (Cr), tantalum (Ta), molybdenum (Mo), andzirconium (Zr). The second metal film 154 can be formed by sputtering orvacuum deposition as in the case of the first metal film 152. In thestructure shown in FIG. 4A, a Zn film having a coefficient of thermalexpansion of about 40×10⁻⁶ deg⁻¹ and a thickness of 200 Å was formed asthe first metal film 152, and an Au film having a coefficient of thermalexpansion of 14×10⁻⁶ deg⁻¹, a thickness of 200 Å and a good elongationcharacteristic was formed as the second metal film 154. The Te₅₀ C₃₀ H₁₅N₅ layer 10 was formed by sputtering a Te target in a mixture gas plasmasubstantially consisting of CH₄ gas and NH₃ gas in the mixing ratio of4:1. In this case, immediately after the layer 10 is formed, the firstand second metal films 152 and 154 are preferably formed in the samevacuum chamber so as to eliminate the adverse effect of dust or the likein the air.

The structure shown in FIG. 4A is subjected to laser irradiation in asimilar manner to that shown in FIG. 1B. However, the power of thecontinuous modulated beam was 10 mW in this case. Upon laserirradiation, scanning electron microscope observation revealed that acontinuous spiral protuberance track 156 having a uniform height of 0.1μm and a bottom width of 1.1 μm was formed on the portion of anuppermost Au film 154' which had been irradiated with the laser beam.For the purpose of comparison, structures were prepared in which a Znfilm of 200 Å thickness alone and an Au film of 200 Å thickness alonewere formed on respective layers 10. When these structures were exposedto laser beam irradiation in the same manner as described above, theheight of the protuberance could not made to exceed 0.05 μm in theformer case and 0.03 μm in the latter case, irrespective of laser beamconditions such as the linear velocity of the table, the power of thelaser beam, or the like. As a consequence, the present inventors wereconvinced of the importance of the bilayered structure of the fourthembodiment.

The first metal film 152 may be made of Sb, Tl, Mg, Al, Mn, Ag, or thelike, which have coefficients of thermal expansion of 37×10⁻⁶ deg⁻¹,28×10⁻⁶ deg⁻¹, 26×10⁻⁶ deg⁻¹, 24×10⁻⁶ deg⁻¹, 22×10⁻⁶ deg⁻¹, and 20×10⁻⁶deg⁻¹, respectively. The second metal film 154 may consist of Pd, Pt,Ti, Ta, Cr, Mo, Zr, or the like, which have coefficients of thermalexpansion of 12×10⁻⁶ deg⁻¹, 9×10⁻⁶ deg⁻¹, 9×10⁻⁶ deg⁻¹, 7×10⁻¹, 6×10⁻⁶deg⁻¹, 5×10⁻⁶ deg⁻¹, and 5×10⁻⁶ deg⁻¹, respectively. It was confirmedthat protuberances of satisfactory shape and having a height of 0.07 μmor more could be formed with any combination of these materials. Afterirradiation, a second highly adhesive layer 16 and a highly releasablelayer 18 were sequentially stacked on a resultant structure 150' shownin FIG. 4B to obtain a stamper structure 158 with a continuous spiralprotuberance 160.

In the fourth embodiment described above, the protuberance 156 is formedon the basis of the pressure of the gas component discharged from theradiation-sensitive layer 10 in accordance with the laser beamirradiation and the difference between the metal characteristics of thefirst metal film 152 as an interlayer and the second metal film 154 asan uppermost layer. Consequently, a protuberance of desired shape(height, width) can be easily formed. When a metal film 154 having goodelongation characteristic is directly formed on the radiation-sensitivelayer 10 which discharges a gas component upon absorption of heatenergy, the shape of the protuberance (particularly its height) isdetermined largely depending upon the pressure of the gas component fromthe underlying layer 10. In contrast to this, when the metal film 152 asan interlayer is formed between the layer 10 and the film 154 as in thefourth embodiment, the height of the protuberance 156 may be increased.If the metal film 154 having a good elongation characteristic is notformed and the film 152 alone is formed on the layer 10, a protuberanceof a great height may be obtained. However, the protuberance shrinksover time after laser beam irradiation is terminated. Thus, by formingthe second metal film 154 having a good elongation characteristic on thefirst metal film 152, such shrinkage of the protuberance may beprevented and a protuberance of good shape may be semipermanentlystabilized. The shape of the protuberance 160 of the stamper 158 can becontrolled with good precision.

Although the present invention has been shown and described with respectto particular embodiments, various changes and modifications which areobvious to a person skilled in the art to which the invention pertainsare deemed to lie within the spirit and scope of the invention.

In the embodiments described above, the record carrier body wasirradiated with a laser beam to form a continuous spiral locus therebyforming a continuous spiral protuberance track. If the body is directlyused as a stamper, optical disks can be manufactured which have spiralpre-grooves and which allow digital write/read of desired information ata user side.

However, the present invention is not limited to this. For example, if astamper is prepared by radiating the body with a pulse modulated laserbeam for digitally representing desired information, read-only opticaldisks storing such information therein can be manufactured.

In the radiation-sensitive layer of this invention, a suitable organiccompound containing an element which may be readily vaporized below apredetermined temperature may be plasma-polymerized to a metalliccompound formed by using the known evaporation technique in order toprepare the radiation-sensitive layer. The radiation-sensitive layer ofthis invention may also be formed by using a plasma assist-CVD (chemicalvapor deposition) technique using an organic metal compound made of asuitable metallic element and an element which is readily vaporizedbelow a predetermined temperature, such as C, H or the like.

What is claimed is:
 1. A method for manufacturing a stamper structurewhich is used to manufacture optical disks, comprising the steps of:(a)preparing a disk-shaped carrier body which has a radiation-sensitivelayer which serves as a single recording layer which absorbs energyfroma beam with which said layer is irradiated and which locally expandsand deforms due to discharging of a gas component contained therein, asubstrate for supporting said radiation-sensitive layer, and a firstadhesive layer which is interposed between said substrate and saidradiation-sensitive layer and which adheres said radiation-sensitivelayer to said substrate; (b) additionally providing said carrier bodywith a metal layer, which has a releasability sufficient to easilyseparate it from a disk substrate made of a preselected material formanufacturing optical disks, and a second adhesive layer which isprovided between said radiation-sensitive layer and said metal layer andwhich has an adhesion strength sufficient to effectively adhere saidmetal layer to said radiation-sensitive layer; (c) irradiating, aftersaid metal layer and said second adhesive layer are additionallyprepared, a focussed radiation beam to form on said carrier body a spothaving a diameter of the order of microns, in a manner as to cause saidradiation-sensitive layer to absorb energy of the beam and deform due tothe discharging of the gas component, thereby forming a protuberance insaid metal layer of said carrier body; and (d) directly using thecarrier body having said protuberance as a stamper structure formanufacturing optical disks each of which comprises a substrate in asurface of which a groove corresponding in shape to the protubuerance isformed.
 2. The method according to claim 1, wherein a laser beam isirradiated onto the carrier body having said metal layer and said secondadhesive layer which are additionally formed on said radiation-sensitivelayer.
 3. The method according to claim 1, wherein a specific metallayer which has high releasability sufficient to be easily separatedfrom disk substrates made of a resin is used as said metal layer, saidsecond adhesive layer being interposed between said radiation-sensitivelayer and said specific metal layer.
 4. The method according to claim 1,wherein said step of forming said protuberance on said carrier bodyincludes the step of:rotating said carrier body while irradiating saidcarrier body with a laser beam of a substantially uniform intensity soas to form, on said rotating carrier body, said protuberancecorresponding to a desired pre-groove serving as a track of the opticaldisks.
 5. The method according to claim 4, wherein said step of formingsaid protuberance on said carrier body includes the step of:rotatingsaid carrier body while irradiating said carrier body which is beingrotated with a continuous laser beam and moving the continuous laserbeam in a radial direction of said carrier body, thereby forming acontinuous spiral protuberance on said radiation-sensitive layer of saidcarrier body.
 6. The method according to claim 1, wherein said step offorming said protuberance on said carrier body includes the stepof:rotating said carrier body while radiating a pulse-modulated laserbeam digitally representing information onto said rotating carrier body,thereby forming a plurality of said protuberances on saidradiation-sensitive layer of said carrier body, whereby when saidcarrier body is directly used as a stamper structure, read-only opticaldisks with data pre-pits are manufactured.